BOX issues Area Forecast Discussion (AFD) at Oct 9, 1:56 PM EDT032
FXUS61 KBOX 091756
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
156 PM EDT Wed Oct 9 2024
.SYNOPSIS...
Dry and seasonable conditions will continue today. A cold front
may bring a few brief showers to northern MA this evening,
otherwise the front will be followed by gusty NW winds and
cooler than normal temperatures for Thursday. Temperatures
moderate Friday, and especially Saturday, when highs may reach
into the 70s. Low pressure approaching from the Gt Lakes will
bring an increasing risk of rain with cooler temperatures
Sunday into Sunday night. Showers may linger into Monday.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1100 AM Update:
Forecast for now looks on track and didn't make significant
changes with this update. Westerly breezes, dry weather and
mostly sunny conditions characterize conditions across Southern
New England. A potent shortwave disturbance in midlevels was
working through north-central Ontario and is expected to cross
into the Northeast. That should bring at least an increase in
cloudiness for the afternoon, greater in coverage north and
west.
However, I am monitoring the potential for possible showers in
portions of central and southern MA/RI later this afternoon, as
the dynamic support tied to the mid/upper shortwave increases.
There are a few HREF CAM members which show isolated showers in
central and southern MA/RI around rush hour, with more scattered
shower coverage progged to our north and west in eastern NY,
southern VT and perhaps into the Berkshires later this
afternoon. If these convective showers materialize as these
solutions indicate they might, they would in all likelihood not
be impactful but we'd need to introduce mention of showers in
the forecast. Will let observed trends and the incoming 12z
guidance dictate the need for those changes so for now, have
maintained dry weather but this is something that I'm keeping a
close eye on with subsequent fcst updates.
Previous Discussion:
Fairly robust mid level shortwave moving into SNE early this morning
with a few showers developing ahead of it across CT. CAMs are
showing some intensification of the showers across SE MA and Cape/
Islands during the pre-dawn hours likely enhanced by the low level
convergence along the surface boundary and area of enhanced moisture
near SE New Eng coast. These showers will be exiting the outer Cape
and Nantucket just after daybreak.
Weak subsidence and drying behind this shortwave will result in lots
of sunshine this morning which will become mixed with diurnal CU
this afternoon, especially interior. A second and stronger shortwave
dropping south from the Gt Lakes will move into northern NY late
today. Showers associated with this feature will be confined to
northern NY and northern New Eng, but it is possible a few showers
could spill into western MA late in the day. Slight cooling noted in
the low levels so it should be a few degrees cooler today with highs
low-mid 60s, with upper 50s higher terrain and modest west
breezes.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Tonight...
The stronger shortwave moves south into SNE this evening with good
cooling aloft, especially across northern MA where a few showers are
possible. Some of these showers may clip the outer Cape overnight
with the upper trough passage. Otherwise, looking at mainly
conditions. The passage of the upper trough and cold front will be
accompanied by brief gusty NW winds which will usher in a cooler
airmass as 850 mb temps drop to 0 to -2C by 12z Thu. Lows will fall
into the upper 30s to low-mid 40s, but milder Cape/Islands.
Thursday...
The upper tough axis and shortwave moves to the east as high pres
pres builds over the Gt Lakes. The column is dry and mostly sunny
skies expected, although diurnal CU will develop under the residual
cold pool aloft. 850 mb temps will remain between 0 and -2C so highs
will be several degrees below normal, generally 55-60, but cooler
higher terrain. The cooler temps will be accompanied by somewhat
gusty NW winds 15-25 mph at times.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Key Points:
* Temperatures normal to slightly above normal Fri/Sat with a trend
toward slightly below normal temperatures by early next week
* Dry weather pattern likely prevails through much of the weekend
with next chance to precipitation potentially arriving by late
Sunday.
Details:
Thursday Night and Friday:
The upper level ridge pattern and NW flow aloft gradually
transitions to more a more zonal pattern. Surface high pressure
persists with the main surface high to the south and west of the
region. This will support dry conditions with minimal cloud cover
overnight. Although the main portion of the cold pool will be lifted
north of the region, this should still provide favorable conditions
for a chilly night/early AM. Optimal radiational cooling and cooler
airmass aloft will support temperatures dropping into the mid to
upper 30s for a good portion of southern New England. Coastal areas
and urban centers trend slightly warmer in the low to mid 40s. With
light NW winds, we'll have to watch the potential for frost
development. Model soundings aren't highlighting considerably low
dewpoint depressions which would limit frost potential, but it
warrants some monitoring for those who have sensitive plants/crops.
With the cooler air aloft pushed out, Friday will trend warmer with
highs rising back into low/mid 60s.
Friday Night - early next week:
The weekend will feature zonal flow aloft with the passage of a few
shortwave troughs embedded in the flow. There are still
differences in timing/strength of the waves. As far as our next
shot at rain, ensemble guidance shows a general consensus on
late Sun-Mon timeframe. Temperatures trend warm for Saturday
with highs slightly above normal in the upper 60s/low 70s.
Otherwise, Sunday through early next week stay around to
slightly below normal.
&&
.AVIATION /18Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18Z TAF Update:
Through 00z Thursday: High confidence.
VFR. A low (<15%) chance at a passing shower, but if any develop
they would not be strong enough to yield any restrictions. Left
out of the TAF for now due to low confidence. W/WNW winds around
10-12 kt.
Tonight: High confidence.
SCT-BKN VFR ceilings. Cold front moves through between 07-11z
Thursday and brings a windshift to NW around 10-15 kt with
sub-20 kt gusts.
Thursday: High confidence.
Mainly VFR, though out on the Outer Cape during the morning
hours we could see ceilings get near MVFR levels due to ocean
effect. NW winds 10-15 kt with gusts 20-25 kt.
Thursday Night: High confidence.
VFR. Gusts should ease after sundown with NWly sustained winds
decreasing to around 6-10 kt.
KBOS TAF...High confidence in TAF.
KBDL TAF...High confidence in TAF.
Outlook /Thursday Night through Sunday/...
Thursday through Saturday: VFR. Breezy.
Saturday Night: VFR.
Sunday: VFR. Slight chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Today through Thursday: High confidence.
Still dealing with 5-6 ft seas over the eastern MA waters but seas
are subsiding and will drop below SCA this morning. W winds 10-20 kt
today, then a period of 20-25 kt NW gusts possible late tonight into
Thu behind the cold front. May eventually need to consider a SCA for
late tonight into Thu.
Outlook /Thursday Night through Sunday/...
Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft.
Thursday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft.
Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Friday Night through Saturday: Winds less than 25 kt. Areas of
seas approaching 5 ft.
Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Sunday: Winds less than 25 kt. Slight chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...KJC/Mensch
NEAR TERM...KJC/Loconto
SHORT TERM...KJC
LONG TERM...Mensch
AVIATION...Loconto/RM
MARINE...Loconto/RM
Source:
BOX issues Area Forecast Discussion (AFD) at Oct 9, 1:56 PM EDT----------------
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